Yes. Customising buttons is a great way to improve the look and feel of your campaign or event. And its easy too!
From your campaign manager, select Edit Microsite
From there, click on the Buttons tab:
Then, simply select the button you would like to customise. You can customise the colour to match your brand colours or you can load in a button image by clicking the browse button. If you are designing a custom button image, the optimal button image dimensions are 235px wide and 59px high.
When you are done, just update the campaign.